Sharks have been around in some form for about 400 million years. Even before dinosaurs roamed the earth, sharks hunted through the oceans! They're such good survivors that they've had little need to evolve in the last 150 million years. These ancient predators fascinate adults and children alike.

Tampa Bay is an important nursery area for sharks. Bull sharks, for example, give birth near the mouth of the Alafia River, while young blacktip sharks are commonly found in Terra Ceia Bay. Bonnetheads, one of the smaller species, roam the seagrass meadows of the bay, while adult hammerheads and bull sharks patrol deeper waters near passes and channels.

Sharks are members of the elasmobranch family, referring to animals without backbones. Instead, their bodies are composed of lightweight but very strong cartilage. Skates and rays are also elasmobranchs. Most shark species give live birth, although some deposit eggs in egg cases attached to algae or coral.

Sharks can have from 1 to 100 babies at a time, depending on the species. These offspring are called pups. Sharks do not care for their babies after they are born, but they do search for a safe place where they can lay their eggs or give birth.

If you see a shark jump out of the water and spin around several times, you may have spotted a blacktip shark. They are easily confused with spinner sharks; however, the spinner has a more extended snout, smaller fins, and a more slender body. Blacktips are named for the distinctive black markings on the tips of their dorsal fins. They are relatively small members of the shark family, growing to about 7-8 feet. Blacktips are fast swimmers with narrow, pointed snouts, thick grey bodies, and long gill slits.

Sharks of Tampa Bay

Female blacktips become mature at 6 or 7 years old. They mate in the summer and give birth about a year later in late May and June. These sharks typically have less than ten pups, and both newborn pups and juveniles can be found in lower Tampa Bay, mostly in Terra Ceia Bay, during late spring and early fall. The lifespan of blacktip sharks is only about 12 years. Their main food source is fish such as sardines, herring, mullet, jacks and Spanish mackerel. They also like squid, stingrays, anchovies and crustaceans.

The nurse shark is a nocturnal animal that rests on sandy bottoms or in caves or in crevices of rock in shallow waters during the day. Adult nurse sharks generally range from light yellowish tan to dark brown in color. They have two spineless, rounded dorsal fins with the first dorsal fin much larger then the second. The nurse shark is a master of camouflage, and can change colors to match its surroundings, turning darker against darker bottom, and lighter over sand.

Because they grow slowly, and have a slow reproductive rate, sharks are particularly vulnerable to overfishing. Currently, data indicates that more than 100 million sharks are harvested worldwide every year, and many scientists are concerned about the long-term survival of sharks - which play a critical role as "top dog" predators in marine ecosystems.

Research is providing new and fascinating insights into shark behavior. For example, researchers from Mote Marine Laboratory documented an "evacuation" of blacktip sharks from Terra Ceia Bay in the days prior to the arrival of Tropical Storm Gabrielle in 2001. The sharks returned a few days after the storm, leading the scientists to speculate that changes in barometric pressure associated with the storm prompted the sharks to flee the area temporarily.

Mote is attaching tags to sharks in the bay to learn more about their movement, and also has set up several underwater acoustic listening stations to assist with tracking tagged sharks.

As scientists learn more about the sharks of Tampa Bay, myths will be dispelled. According to Mote Marine, one myth is that sharks are scavengers. This is not true; they are carnivores or meat eaters. They live on a diet of fish and sea mammals like dolphins. Sharks even eat other sharks. For example, a tiger shark might eat a bull shark, a bull shark might eat a blacktip shark and a blacktip shark might eat a dogfish shark! It's a shark-eat-shark world under the seas.

Fortunately, humans are not on the preferred menu of sharks. Sharks do not normally attack humans, and the vast majority of shark bites are a case of mistaken identity.

Although you are 30 times more likely to be struck by lighting than attacked by a shark, it is a good idea not to swim in murky water or have a stringer of fish attached to your waist while wade fishing.